Water Supply Trade-Off Analysis
Tradeoff analysis involves determining the effect of decreasing one or more key factors and simultaneously increasing one or more other key factors in a decision model. This is a systematic approach to balancing the trade-offs between objectives such as minimizing cost and maximizing performance. In this particular model, 3 objectives are taken into consideration including cost, reliability, and sustainability. Cost is a function of capital, operational, and maintenance costs. Reliability is a function of water supply yield, peak flow, and number of users affected. Sustainability is a function of effects on the environment, ease of use, and public perception.
Description
A series of measuring weights are applied to the categories of decision criteria to quantify a normalized score. The scores can be viewed by category or as a summary for the entire project. This model evaluates the scores of 4 different water supply scenarios, including:
- minimal approach
- added groundwater
- a new desalinization plant
- a new reservoir
An input page is accessed by clicking on the "Input" button where you can edit the future supply options, unit costs, and water quality goals. A measure page is accessed by clicking the "measures" page where you can adjust the tradeoff factors and view results of the model.
As shown in the schematic, the first step is to develop some alternative water supply scenarios followed by simulating the system. In this simple example, an assumed water demand is applied to the multiple supply alternatives, each of these provide a different measure of reliability and sustainability with different applied capital costs to build the water supply facilities. The water supply simulation model is run as a Monte Carlo so that the reliability can be determined. Upon simulation, the alternatives are evaluated by policy objectives (cost, reliability, and sustainability), then weights are applied for multiple criteria. Utility curves are used to normalize the criteria scores to estimate the utility scores upon which the alternatives can be compared to one another.
Further refinement of the alternatives can take place and then run through the process again to attempt at higher utility scores.
Article on water supply trade-off analysis:
http://www.waterresearchfoundation.org/research/TopicsAndProjects/projectProfile.aspx?pn=3003Download the model file
Screen Captures of the Model:
Trade-off controls:
Result plot comparing the final scores of each alternative:
See Also
